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We report the effect of strontium (Sr) doping on dielectric, magnetization, and thermodynamic properties of polycrystalline Y1-xSrxMnO3 (x = 0.1, 0.2) samples prepared by conventional solid-state reaction method. The temperature dependent dielectric permittivity and specific heat curves noticeably show the anomalies near its magnetic transition point, i.e., Neel temperature (TN), which are probably generated by the frustrated Mn3+ spins (S = 2) on a triangular Mn lattice showing the magneto-electric coupling between the electric and magnetic orders. However, the magnetic transition is not clearly evident in the magnetic susceptibility due to the frustration on the Mn triangular lattice and the dominating paramagnetic susceptibility of the Y3+ spins. The electronic transport mechanism in these materials was analyzed within the framework of conventional Arrhenius Law, i.e., ρ(T) = C exp(Ea/kBT) applied to low frequency ac resistivity data, and through the peak method employed to the permittivity and loss tangent by using equation f = f0 exp(-Ea/kBTp), suggests simple thermal activation. The effect of induced Mn4+ ions in the crystal lattice with doping of Sr2+ ion on transport properties has been discussed in details. [ABSTRACT FROM AUTHOR]

Magnetotransport and thermal studies of Pr2/3Sr1/3MnO3 polycrystalline sintered bulk sample are reported here. The resistivity ρ(T) and thermoelectric power S(T) data show an insulator to metal (I-M) phase transition at TP≈294 K and TS≈290 K, respectively. Magnetization measurement confirms that the sample undergoes a transition from paramagnetic to ferromagnetic phase at a defined Curie temperature TC=280 K. A substantial increase in magnetoresistance from 2.5% at 280 K to 5% at 77 K has been noticed in a low magnetic field 0.15 T. Small polaron hopping model is found to be operative above the transition temperature TP, whereas electron-electron and electron-magnon scattering processes govern the low temperature metallic behavior. A detailed analysis of thermoelectric power in the ferromagnetic regime suggests that the complicated temperature dependence of S may be understood on the basis of electron-magnon scattering. A transition from decreasing high temperature thermal conductivity (due to local anharmonic distortions associated with small polarons), to an increasing thermal conductivity (due to decreasing of phonon-phonon scattering) and thereafter a peak at ∼100 K (signifying a crossover from Umklapp to defect-limited scattering) have also been noticed. Specific heat measurements depict a pronounced anomaly near the TC, indicating the magnetic ordering and magnetic inhomogeneity in the sample. [ABSTRACT FROM AUTHOR]

We report on measurements of the temperature dependence of the electrical resistivity (ρ), thermopower (S), and thermal conductivity (κ) of Ti-Zr-Ni alloys between 10 and 300 K. A series of Ti-Zr-Ni quasicrystals (QCs) Ti40Zr40Ni20, Ti45Zr35Ni20, and Ti50Zr30Ni20 and metallic glasses Ti35Zr45Ni20 and Ti40Zr40Ni20 was prepared to systematically study the compositional and structural dependences of their transport properties. The resistivity of all these alloys was found to be very weakly temperature dependent with a negative temperature coefficient of resistance. Further, the observed increase in electrical resistivity with increasing Ti/Zr ratio is most likely due to the increase in disorder. The S/T against temperature curves exhibited a maximum between 20 and 50 K and a noticeable deviation from the expected linear behavior in S(T) at higher temperatures. Such observations in the thermopower of QCs have been attributed to the electron-phonon enhancement and phonon drag effect. The measured thermal conductivities were analyzed by separating the electronic and phonon contributions that provide a reasonable explanation for plateau-type feature in κ(T) of QCs. Our present results suggest that the transport properties of glassy phase are influenced by the same mechanisms as those of quasicrystalline phase. [ABSTRACT FROM AUTHOR]

We report the structural and electron transport properties of a series of compounds where A/B-site substituted Ni-deficient La(Ni0.6Fe0.3)O3 compounds with A=Ag+, Pb2+, Nd3+ and B=Mn3+, Ga3+ have been synthesized by a chemical route. Electrical resistivity was used as an indicator to explore the response of La(Ni0.6Fe0.3)O3 for different A/B-site substitutions. The rationalized explanation for the variations of resistivity with substitutions was based on the change in bond length and modification of band structure due to substitutional disorder. A variable range hopping conduction approach is employed to explain the temperature variation of resistivity, and the result suggest that disorder-induced localization of charge carriers dominates the electrical transport in these compounds. [ABSTRACT FROM AUTHOR]

We report the structural and electron transport properties of a series of compounds where A/B-site substituted Ni-deficient La(Ni0.6Fe0.3)O3 compounds with A=Ag+, Pb2+, Nd3+ and B=Mn3+, Ga3+ have been synthesized by a chemical route. Electrical resistivity was used as an indicator to explore the response of La(Ni0.6Fe0.3)O3 for different A/B-site substitutions. The rationalized explanation for the variations of resistivity with substitutions was based on the change in bond length and modification of band structure due to substitutional disorder. A variable range hopping conduction approach is employed to explain the temperature variation of resistivity, and the result suggest that disorder-induced localization of charge carriers dominates the electrical transport in these compounds. [ABSTRACT FROM AUTHOR]

The electrical, magnetotransport, magnetization and thermal properties of [Pr.sub.2/3][Sr.sub.1/3]Mn[O.sub.3] (PSMO) manganite displaying I-M transition near room temperature are studied. Specific heat measurements have shown a pronounced anomaly near the [T.sub.C], thus indicating the magnetic ordering and magnetic inhomogeneity in the sample.

The synthesis and structural and electron transport properties of the A/B-site substituted Ni-deficient La([Ni.sub.0.6][Fe.sub.0.3])[O.sub.3] perovskites with A=[Ag.sup.+], [Pb.sup.2+], [Nd.sup.3+] and B=[Mn.sup.3+], [Ga.sup.3+] are studied. The electrical transport of these compounds is shown to be completely dominated by the localization of the charge carriers.